Charging devices for inductively transmitting energy are known, for example, from electrical toothbrushes. In future, portable devices such as, for example, mobile phones, MP3 players and the like will also be charged by means of inductive alternating field. Such portable devices have electronics which are capable of deciding whether or not the energy store is to be charged. So that a charging device can recognize whether the portable device which is arranged in the spatial vicinity of the charging device has to be charged at all, the inductive alternating field is switched on for a short time until the portable device, which is introduced into the area of action of the charging device, confirms, through communication with the charging device, the presence and the intention to be charged. This process is referred to as “polling”.